I mean, GrapheneOS hits at least 2/3 of your demands pretty well. The Play services are "regular" apps with permissions that you can take away. For contacts and files you get "scopes", i.e. you decide what the app can see, while the app is left to believe that it can see everything there is.

That said, I think the marketing of GrapheneOS could be better. Every introduction of GrapheneOS I've seen paints the image of Graphene being "Absolute security, no compromises", whereas in reality GrapheneOS is the most "Things need to work, no compromises. Then make the rest as safe as possible" custom ROM that I've used thus far (in particular regarding them allowing you to install Google Play, rather than using MicroG).

I would certainly be using GrapheneOS if only I could get one to run on something else than a Pixel.

I have a perfectly good phone whose bootloader can be unlocked and I can install LineageOS or other AOSP installations there but all I'm aware of and I've researched come short on the sandboxing and permissions. I'd be willing to use GrapheneOS without support for specific security hardware (if only they supported that configuration) just for the features mentioned but Pixel phones are just too expensive. I've always been more than happy with a decent low-tier phone and I don't see a technical reason to change that. Nothing wrong with my phone.

Mock Location exists but our Location Scopes feature will largely replace it for non-development use. Camera, Microphone and other scopes features will be provided too. We haven't fully fleshed out what the ones for other permission groups such as Phone will look like yet but it's planned.